Chemical foaming of water-bearing explosives

ABSTRACT

MAKING FOAMED SEMISOLID COLLOIDAL DISPERSIONS OF WATER-BEARING BLASTING AGENTS CONTAINING AN INORGANIC OXIDIZING SALT, E.G., AMMONIUM NITRATE, FUEL, WATER, AND SEPARATELY INCORPORATING INTO THE MIX EACH COMPONENT OF A TWO-COMPONENT FOAMING AGENT COMPOSITION COMPRISING (A) A HYDRAZINE OR DERIVATIVE THEREOF, AND (B) AN OXIDIZING AGENT THAT AIDS IN DECOMPOSING SAID HYDRAZINE(S).

United States ABSTRACT OF THE DISCLOSURE Making foamed semisolid colloidal dispersions of water-bearing blasting agents containing an inorganic oxidizing salt, e.g., ammonium nitrate, fuel, water, and separately incorporating into the mix each component of a two-component foaming agent composition comprising (a) a hydrazine or derivative thereof, and (b) an oxidizing agent that aids in decomposing said hydrazine(s).

BACKGROUND OF THE INVENTION Semisolid collodial dispersions of water-bearing blasting agents are well known. These products typically comprise an oxidizing component, usually predominantly ammonium nitrate, a fuel component, and water. More particularly, these blasting agents are referred to in the art as water gels or slurry explosives, and emulsion-type blasting agents. The blasting agents commonly referred to as water gels contain, in addition to the above ingredients, a thickening agent that gels the composition, e.g., polyacrylamides. In addition, the water gels may contain high explosives such as TNT or metallic fuels such as aluminum that function not only as part of the fuel component of the blasting agent but also increase explosive strength. Representative water gels of the type disclosed hereinabove are more fully described in US. Pats. 3,153,606, 3,431,155 and 3,288,658. As indicated above, other water-bearing explosive compositions that are semisolid collodial dispersions are known as emulsion type blasting agents. Emulsion-type blasting agents contain an oxidizing agent, water, emulsifying agent and a fuel component that is a carbonaceous compound insoluble in water and is liquid during formation of the emulsion. The emulsifying agent generally forms a water-in-oil emulsion wherein oil is the continuous phase and water is the discontinuous phase of the emulsion. Representative water-bearing semisolid colloidal dispersions of emulsion-type blasting agents are described in US. Pat. 3,447,- 978. Furthermore, these semisolid collodial dispersions of Water-bearing blasting agents, both the thickened water gel and emulsion type, have been prepared in such a manner that small has bubbles are entrapped therein or they contain gas-entrapping material, e.g., microballoons. The inclusion of gas in the form of bubbles or as gasentrapping material is known to regulate the strength of the blasting agent. Methods for preparing gas-containing water-bearing blasting agents include the mechanical incorporation of gas and in situ chemical generation of gas by the decomposition of certain compounds. Although these procedures have produced satisfactory products, there is a need for making foamed semisolid colloidal dispersions of water-bearing blasting agents by employing a foaming agent composition that is simple to use; inexpensive; forms gas bubbles in the blasting agent within a short period of time which bubbles remain formed therein for extended periods of time; forms gas bubbles in the composition that are small, generally the majority of bubbles are not greater than about 100 micron diameter, preferably between to 70 microns, for the most effective sensitivity; provides an effective control over the amount of gas introduced into atent the composition; and is applicable to water-bearing blasting agents, e.g. water gels, and emulsion-type blasting agents.

SUMMARY OF THE INVENTION This invention provides a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents, especially water gels or thickened water-bearing explosives, and emulsion-type blasting agents, which comprises mixing inorganic oxidizing salt, fuel, and Water, the improvement which comprises separately incorporating into the mix each component of a two-component foaming agent composition comprising (a) a hydrazine or derivative thereof, and (b) an oxidizing agent that aids in decomposing said hydrazine or derivative thereof to produce gas, thereby foaming and sensitizing the blasting agent, with the proviso that when thickener is added to the mix said thickener is nonoxidizable in the mix during preparation of the blasting agent. When preparing water gels a nonoxidizable thickener is added to the waterbearing blasting agent to thicken or gel the aqueous phase. When emulsion-type blasting agents are prepared, an emulsifying agent and a liquid carbonaceous fuel are added to the water-bearing blasting agent during preparation in order to form an emulsion.

The foaming agent comprises a hydrazine or derivative thereof and an oxidizing agent that decomposes the hydrazines causing them to produce gas and thus foam the composition. Any hydrazine such as hydrazine itself or hydrazine hydrate, or any hydrazine derivative such as substituted hydrazines or hydrazine salts can be used as a component of the foaming agent. The oxidizing agent used as a component of the foaming agent composition is one that decomposes said hydrazine(s), i.e. hydrazine or derivative thereof, during preparation of the blasting agent and causes the hydrazine or derivative thereof to produce gas thereby foaming the blasting agent.

DESCRIPTION OF PREFERRED EMBODIMENTS The composition employed as the foaming agent that is used in the process of this invention comprises two components, namely, a hydrazine or derivative thereof and an oxidizing agent therefor. The hydrazines decompose in the blasting agent in the presence of the oxidizing agent and give off gas at temperatures at which the ingredients of the blasting agent are formulated thus producing a foamed product that is sensitized due to the presence of small gas bubbles. Any hydrazine, such as hydrazine itself or hydrazine hydrate, or hydrazine derivatives will function satisfactorily as a component of the foaming agent. Preferably, the hydrazine derivative is water soluble because such compounds increase the rate of reaction of gas formation in the blasting agent. Representative hydrazine derivatives that can be used in the process of this invention include substituted hydrazines, particularly those having the formulae or RR' =NNH' wherein R and R represent alkyl radicals, especially those having 1 to 5 carbon atoms; aryl radicals, especially those containing 6 to 8 carbon atoms; alicyclic radicals, especially those containing 5 to 8 carbon atoms, and hydrazine salts. Especially effective alkyl and aryl hydrazines or combinations thereof that can be used in the present process include methyl hydrazine, ethyl hydrazine, propyl hydrazine, phenyl hydrazine, diphenyl hydrazine and methyl-phenyl hydrazine. Effective alicyclic hydrazines that are readily available and can be used in the process of the invention include cyclohexyl hydrazine and cyclopentyl hydrazine. Hydrazine derivatives containing a carbonyl group such as semicarbazide can also be used as a component of the foaming agent in this process. Representative organic and inorganic hydrazine salts that can be used in the process of this invention are hydrazine nitrate, hydrazine sulfate, dihydrazine sulfate, hydrazine chloride, hydrazine phosphite, hydrazine phosphate, hydrazine perchlorate, hydrazine formate, hydrazine acetate, hydrazine oxalate and hydrazine tartrate. In general, an important point to remember in selecting a hydrazine derivative for use in the present process is to employ compounds that contain an NH-NH or =N-NH radical, since it is this moiety that gives off gas to foam the composition. Due to ease of handling, water solubility and commercial availability, best results are obtained when hydrazine hydrate, monomethyl hydrazine or phenyl hydrazine are used in the process of this invention. The amount of hy drazine or derivative thereof that is added to the mix is about from 0.01 to 3%, preferably 0.05 to 1%, based on the weight of the total composition of the blasting agent.

Any oxidizing agent for the hydrazines can be used as a component of the foaming agent composition. Representative oxidizing agents that can be used in the process of this invention in combination with the hydrazines to sensitize and foam the blasting agent include hydrogen peroxide, chromium trioxide, and the persulfates, permanganates, chlorates, iodates, bromates, dichromates, and chromates of ammonium, alkali, and alkaline earth metals and the soluble salts of Group IB metals of the Periodic Table, especially the copper salts. Especially good results are obtained when hydrogen peroxide, ammonium persulfate or copper nitrate are used as oxidizing agent for the hydrazines. The amount of oxidizing agent used in combination with said hydrazines can vary over a wide range. The amount employed depends upon the molecular weight of the oxidizing compound and the electron change that occurs. Preferably, about a stoichiometric amount of oxidizing agent is used with the particular hydrazine or derivative thereof. However, if one desires the blasting agent to foam at a slower rate, less than the stoichiometric amount of oxidizing agent is added and, on the other hand, if rapid foaming is desired, more than the stoichiometric amount of oxidizing agent is used with the hydrazines. For most purposes the amount of oxidizing agent added is from about the stoichiometric amount to in excess. Of course, larger quantities can be used but in most instances it is not needed and wasteful.

The two components comprising the foaming agent must be added to the composition separately. Any order of addition is satisfactory but preferably the oxidizing component is added before the hydrazine or derivative because they are added at a time when the mix has thickened or the emulsion has formed so that the composition is sufiiciently viscous to retain gas bubbles when foaming occurs. Both ingredients of the foaming agent composition can be added to the mix at ordinary mixing temperatures, usually between 90 to 170 F., and a satisfactory product is obtained. Most preferably, the temperature of the mix during addition of each component of the foaming agent is from 100 to 130 F. The hydrazine(s) and its oxidizing agent cannot be mixed together prior to their addition to the inorganic oxidizing salt mixture; the components making up the foaming agent must be separately incorporated in the mix.

The inorganic oxidizing salts used in this invention are those conventionally used in water-bearing blasting agents and include ammonium, alkali metal and alkaline earth metal nitrates and perchlorates as well as mixtures of two or more such salts. Representative inorganic oxidizing salts are ammonium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, ammonium perchlorate, sodium perchlorate, potassium perchlorate and magnesium perchlorate. The amount of inorganic oxidizing salt used in the water-bearing blasting agents is from about to 75% by weight of the composition. Preferably, a mixture of inorganic nitrate salts is used of which at least about 45% by weight of the total composition is ammonium nitrate and of the order of 15 to 25%, preferably about 15%, based on the weight of the total composition, is sodium nitrate.

As mentioned above, the foamed semisolid colloidal dispersion of water-bearing blasting agents can contain a thickening agent to get the composition, thus forming the well-known blasting agents known as water gels or slurry explosive compositions. However, the thickening agent used in the process of this invention must be non oxidizable in the mix during formation of the blasting agent. By nonoxidizable thickening agent is meant one that is not oxidized by the hydrazine oxidizing agent component, e.g. hydrogen peroxide, of the foaming agent, or other ingredients used in the water gel during preparation of the blasting agent. Representative thickening agents that are not oxidized during manufacture of the blasting agent that can be used in the process include polyvinyl alcohol, polyacrylamides, high molecular weight polyethylene oxides, silica gels, starches and modified starches such as dextrins and hydroxyethyl starch, water-diseprsible derivatives of cellulose such as methyl cellulose, sodium carboxymethyl cellulose, as well as mixtures of two or more of the above nonoxidizable thickening agents. Preferably, the thickening agent used in the process is polyacrylamide. The amount of nonoxidizable thickening agent added regulates the consistency of the blasting agent and such thickeners are used in amounts ranging from about 0.2 to 5%.

In addition, as mentioned above, this invention is applicable to the production of emulsion-type water-bean ing blasting agents. These compositions contain, in addition to inorganic oxidizing salt, water and fuel, an emulsifying agent. The amount of emulsifying agent used is from about 0.5 to 10% by weight, and preferably from about 1 to 2%. Larger quantities of emulsifying agent may be added since excess emulsifying agent merely serves as a supplemental fuel for the blasting agent. Generally, the emulsifying agents used are those that form water-in-oil emulsions such as sorbitan fatty acid esters, e.g., sorbitan monolaurate, palmitate or oleate; polyoxyethylene sorbitol esters and long chain fatty acids and esters thereof, so that a water-iu-oil emulsion of the blasting agent is formed. Especially good results are obtained when the emulsifying agent is a stearate salt, e.g., sodium stearate, alone or in combination with stearic acid. Other emulsifying agents include sodium oleate with or without oleic acid, dodecylbenzene sulfonic acid and tall oil amides such as the tall oil amide of tetraethylene pentamide, referred to as EZ-Mul, manufactured by the Baroid Division of National Lead Co.

The fuels used in thickened water gel blasting agents containing nonoxidizable thickener include self-explosive fuels, nonexplosive fuels and metallic fuels as well as mixtures of the aforementioned types of fuels. Representative self-explosive fuels that can be used in the composition are organic nitrates, nitro compounds and nitramines such as trinitrotoluene, pentaerythritol tetranitrate, tetranitro- N-methylaniline, nitrostarch, explosive grade nitrocellulose, smokeless powder and mixtures thereof. Generally, the amount of self-exposive fuel is from 10 to 40% by weight, based on the weight of the composition. Nonexplosive fuels such as certain nitro aromatic hydrocarbons, for example, monoand dinitrobenzenes can be used, and sulfurous fuels including sulfur itself. Carbonaceous fuels such as finely-divided coal, hydrocarbons such as fuel oil and paraflin wax, can be added to the composition. Metallic fuels can also be used and these include light elements such as aluminum, magnesium, boron and silicon, both singly and in combination. Heavier metallic compounds and alloys including ferrophosphorus and ferrosilicon can be added to the mix. Blasting agents of the emulsion type wherein a water and oil emulsion is formed must contain a carbonaceous fuel that is liquid during formation of the emulsion. The carbonaceous fuel is not soluble in water and generally forms the continuous phase of the emulsion so that the blasting agent is in the form of a water-in-oil emulsion. The carbonaceous fuel used in the emulsiontype blasting agents can comprise oil alone, a wax and oil, a wax and a polymeric material, or a wax and a polymeric modified oil component. The fuel used thus includes hydrocarbons such as paraffinic, olefinic and aromatic that are saturated or unsaturated. Waxes that can be used include paraflin wax and mineral waxes. Petroleum oil of varying viscosities can be used as the fuel, especially fuel oil. Polymeric materials such as natural or synthetic rubber may be used as a carbonaceous fuel component. Preferably, the fuel comprises oil alone, especially No. 2 fuel oil. Generally, the amount of fuel used is from about 3 to 10% by weight. Optionally, the emulsiontype blasting agents can contain supplementary fuels, as disclosed hereinabove, especially particulate metals, e.g., aluminum and finely-divided coal. In general, the amount of fuel used in the blasting agents of the present invention is such that the oxygen balance of the blasting agents will be from --25 to +10% and preferably from l to +5 The amount of water used in the blasting agents of the thickened water gel and emulsion type is from 5 to 30%, preferably about from to water is used in preparing thickened water gels and emulsion-type blasting agents.

Optionally, other ingredients can be incorporated in the mix for formulating the blasting agents. For example, nitrogen-base salts can be added to the water-bearing blasting agents to increase their effectiveness. The nitrogen-base salt functions, among other things, as a fuel component and such salts that can be used in this invention are disclosed, for example, in US. Pat. 3,431,155. Preferably, the nitrogen-base salts used are monomethylammonium nitrate and ethylenediammonium dinitrate. Such salts are added in amounts of from about 5 to 40% by weight. As is conventional in the preparation of thickened water gels, the composition can also contain a crosslinking agent such as an alkali metal dichromate or a soluble antimony compound, e.g., potassium antimony tartrate, in amounts of from 0.001 to 1% by weight. Likewise, a crystal habit modifier for the inorganic oxidizing salt such as Petro AG, which is a derivative of naphthalene sulfonic acid salts, can also be added to water gel compositions, if desired.

A procedure for making thickened water gels is as follows: The oxidizer salts and other water-soluble materials are mixed with water at temperatures usually between about 140 to 170 F. to effect maximum solubility. The crosslinking agent, and one component of the foaming agent composition, usually the hydrazine oxidizing agent are added. The addition of these ingredients cools the mix. Subsequently, the mixture is agitated briefly and nonoxidizable thickener added. Mixing is continued until thickening occurs and the second component of the foaming agent composition is added. Preferably, the mix at addition of the last component, e.g. hydrazine hydrate or derivative thereof, has a temperature of about from 100 to 130 F. The composition is mixed for about seconds and then the crosslinking agent is added and a thickened foamed blasting agent sensitized with gas bubbles is obtained.

A procedure for making emulsion-type blasting agents involves mixing the inorganic oxidizing salts, e.g., an aqueous solution of ammonium nitrate, and sodium nitrate and other water-soluble materials at about 120 to 190 F. to form a solution. The carbonaceous fuel, e.g. fuel oil, emulsifying agent and an oxidizing agent for a hydrazine, e.g., hydrogen peroxide, are added to the salt solution. The ingredients are mixed and when the emulsion starts to form and thus thicken a hydrazine, such as hydrazine hydrate, is added thereto and, subsequently, the foaming agent in the composition forms small gas bubbles therein. Preferably, the temperature of the emulsion is usually between about to when foaming occurs.

The following examples further illustrate the invention in detail.

EXAMPLE 1 Formulation: Percent by weight Monomethylammonium nitrate (86%) 47.3 Ammonium nitrate (75%) 20.7 Sodium nitrate 18.8

Water 5.7 Sodium stearate 1.0 Fuel oil 4.8 Stearic acid 0.5 Hydrogen peroxide solution (3%) 1.0 Hydrazine monohydrate sol. (85%) 0.2

The monomethylammonium nitrate and ammonium nitrate, both as aqueous solutions of the indicated strength, were mixed with the sodium nitrate, water, and sodium stearate such that the resultant composition had a temperature of -150 F. Separately, the fuel oil and stearic acid, previously mixed together, were mixed with the aqueous solution along with the hydrogen peroxide. When, on mixing, the emulsion began to form, and the temperature of the mix was about 130 F., the hydrazine monohydrate was added. The resulting foamed emulsiontype blasting agent contained small gas bubbles having diameters between about 20 to 60 microns and had a specific gravity of 1.26. The material at 40 F. compressed a lead block 2% inches and at 40 F. had a detonation velocity of 5200 m./sec.

EXAMPLE 2 Formulation:

Water percent by weight 15.0 Ammonim nitrate do 36.0 Sodium nitrate do 14.6 Monomethylammonium nitrate do 29.4 Coal do 3.0 Thickener (polyacrylamide) do 2.0 Crosslinking agent: Sodium dichromate soln.,

5% rnl./kg 6.0 Hydrazine monohydrate soln., 85% ml./kg 2.0 Ammonium persulfate g./kg 2.5

The amine nitrate, sodium nitrate and ammonium nitrate were dissolved in water at 170 F. The nonoxidizable thickener premixed with the coal was added to the nitrate solution. The mix was cooled to 100 F., ammonium persulfate was added and the mix allowed to thicken for 4 minutes, then hydrazine monohydrate was added. The composition was mixed for about 30 seconds and crosslinking agent added.

The specific gravity of the resulting foamed water gel blasting agent containing gas bubbles having diameters between about 20 to 60 microns was 1.15. The blasting agent detonated at 40 F. and gave a lead block compression of 2% inches. The same formulation unfoamed (specific gravity=1.45) failed to detonate.

EXAMPLE 3 Formulation:

Ammonium nitrate (77%) percent by weight 78.5 Sodium nitrate do 15.0 Fuel oil do 5.0 Sodium stearate do 1.0 Stearic acid do 0.5 Hydrogen peroxide, 3% ml/kg" 10.0 Monomethyl hydrazine m1./kg 1.9

The ammonium nitrate (as an aqueous solution of the indicated strength) was mixed with the sodium nitrate such that the resultant solution had a temperature of F. when all of the sodium nitrate was dissolved. The sodium stearate, stearic acid, fuel oil and hydrogen peroxide were added with mixing. When, during the mixing,

an emulsion started to form, the monomethyl hydrazine was added. The resultant foamed emulsion had a specific gravity of 1.2, and the material at 45 F. was detonated to compress a lead block 2% inches.

EXAMPLE 4 A foamed emulsion was prepared as described above in Example 3 except that 3.5 ml. of phenyl hydrazine was substituted for the monomethyl hydrazine. The product had a specific gravity of 1.3 and, at 45 F., compressed a lead block 2 inches.

EXAMPLE 5 A foamed emulsion was prepared as described above in Example 3 except that 2.7 ml. of l,ldimethyl hydrazine was substituted for monomethyl hydrazine.

The product had a specific gravity of 1.20, and, at 45 F., compressed a lead block 2% inches.

EXAMPLE 6 Formulation:

Ammonium nitrate (77%) percent by weight 78.5 Sodium nitrate do 15.0 Fuel oil do 5.0 Sodium stearate do 1.0 Stearic acid do 0.5 Hydrazine, 85% ml./kg 3.0 Cu(NO -3H O, 85% aq. solution g./kg 1.0

The ammonium nitrate (as an aqueous solution of the indicated strength) was mixed with the sodium nitrate such that the resultant solution had a temperature of 160 F. when all of the sodium nitrate was dissolved. The sodium stearate, stearic acid, and fuel oil were admixed with the solution of ammonium and sodium nitrates until an emulsion started to form; At that time the hydrazine (as an aqueous solution of the indicated strength) was added followed by the Cu (II) nitrate trihydrate dissolved in a minimal amount (5 ml./g.) of water. The resultant foamed emulsion had a specific gravity of 1.25 and the material, at 75 F., was detonated to compress a lead block 2% inches.

EXAMPLE 7 A foamed emulsion was prepared as described above in Example 3, except that 2 g./ kg. of semicarbazide hydrochloride and 7 ml./kg. of potassium dichromate (5%) was used in place of monomethyl hydrazine and hydrogen peroxide. Further, the semicarbazide hydrochloride was added with mixing and when the emulsion began to form the potassium dichromate was added. The resulting foamed emulsion had a density of 1.30 g./cc. and the blasting agent at 75 F. compressed a lead block 2 /2 inches.

I claim:

1. In a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents comprising mixing inorganic oxidizng salt, fuel and water, the improvement which comprises separately incorporating into the mix and subsequently mixing therein each component of a two-component foaming agent composition comprising (a) a hydrazine or derivative thereof and (b) and oxidizing agent that aids in decomposing said hydra zine or derivative thereof to produce gas thereby foaming and sensitizing the blasting agent with the proviso that when thickener is added to the mix said thickener is non oxidizable in the mix during preparation of the blasting agent.

2. In a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents comprising mixing inorganic oxidizing salt, liquid carbonaceous fuel, emulsfying agent and water, the improvement which comprises separately incorporating into the mix and subsequently mixing therein each component of a two-component foaming agent composition comprising (a) a hydrazine or derivative thereof, and (b) an oxidizing agent that aids in decomposing said hydrazine or derivative 5 thereof to produce gas thereby foaming and sensitizing the blasting agent.

3. A process of claim 2 wherein the emulsifying agent is one that forms a water-in-oil emulsion.

4. A process of claim 3 wherein the hydrazine derivative is an alkyl hydrazine containing 1 to 5 carbon atoms in the alkyl radical.

5. A process of claim 4 wherein the alkyl hydrazine is methyl hydrazine.

6. A process of claim 3 wherein the hydrazine derivative is an aryl hydrazine containing 6 to 8 carbon atoms in the aryl radical.

7. A process of claim 6 wherein the aryl hydrazine is phenyl hydrazine.

8. A process of claim 3 wherein the hydrazine is hydrazine hydrate.

9. A process of claim 3 wherein 0.01 to 3% by weight of a hydrazine or derivative thereof is added to the mix.

10. A process of claim 3 wherein about a stoichiometric amount of oxidizing agent for the hydrazines or derivatives thereof is added.

11. A process of claim 10 wherein a hydrazine hydrate is added to the mix.

12. A process of claim 11 wherein the emulsifying agent is a stearate salt.

13. A process of claim 3 wherein the hydrazine derivative is semicarbazide.

14. In a process for preparing foamed semisolid colloidal dispersions of water-bearing blasting agents comprising mixing inorganic oxidizing salt, fuel, thickener and water, the improvement which comprises separately incorporating into the mix and subsequently mixing therein each component of a two-component foaming agent composition comprising (a) a hydrazine or derivative thereof and, (b) an oxidizing agent that aids in decomposing said hydrazine or derivative thereof to produce gas thereby foaming and sensitizing the blasting agent containing thickener that is nonoxidizable in the mix during prepara tion of the blasting agent.

15. A process of claim 14 wherein 0.01 to 3% by weight of a hydrazine or derivative thereof is added to the mix.

16. A process of claim 15 wherein about a stoichiometric amount of oxidizing agent for the hydrazines or derivatives thereof is added.

17. A process of claim 16 wherein a hydrazine hydrate is added to the mix.

18. A process of claim 17 wherein the thickener is polyacrylamide.

55 19. A process of claim 18 wherein the oxidizing agent is ammonium persulfate.

20. A process of claim 14 wherein the hydrazine is hydrazine hydrate.

References Cited CARL D. QUARFORTH, Primary Examiner E. A. MILLER, Assistant Examiner U.S. Cl. X.R. 

